1 /*
2  * Copyright (C) 2015 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef AAPT_LINKER_LINKERS_H
18 #define AAPT_LINKER_LINKERS_H
19 
20 #include "Resource.h"
21 #include "process/IResourceTableConsumer.h"
22 #include "xml/XmlDom.h"
23 
24 #include <set>
25 
26 namespace aapt {
27 
28 class ResourceTable;
29 class ResourceEntry;
30 struct ConfigDescription;
31 
32 /**
33  * Defines the location in which a value exists. This determines visibility of other
34  * package's private symbols.
35  */
36 struct CallSite {
37     ResourceNameRef resource;
38 };
39 
40 /**
41  * Determines whether a versioned resource should be created. If a versioned resource already
42  * exists, it takes precedence.
43  */
44 bool shouldGenerateVersionedResource(const ResourceEntry* entry, const ConfigDescription& config,
45                                      const int sdkVersionToGenerate);
46 
47 struct AutoVersioner : public IResourceTableConsumer {
48     bool consume(IAaptContext* context, ResourceTable* table) override;
49 };
50 
51 struct XmlAutoVersioner : public IXmlResourceConsumer {
52     bool consume(IAaptContext* context, xml::XmlResource* resource) override;
53 };
54 
55 /**
56  * If any attribute resource values are defined as public, this consumer will move all private
57  * attribute resource values to a private ^private-attr type, avoiding backwards compatibility
58  * issues with new apps running on old platforms.
59  *
60  * The Android platform ignores resource attributes it doesn't recognize, so an app developer can
61  * use new attributes in their layout XML files without worrying about versioning. This assumption
62  * actually breaks on older platforms. OEMs may add private attributes that are used internally.
63  * AAPT originally assigned all private attributes IDs immediately proceeding the public attributes'
64  * IDs.
65  *
66  * This means that on a newer Android platform, an ID previously assigned to a private attribute
67  * may end up assigned to a public attribute.
68  *
69  * App developers assume using the newer attribute is safe on older platforms because it will
70  * be ignored. Instead, the platform thinks the new attribute is an older, private attribute and
71  * will interpret it as such. This leads to unintended styling and exceptions thrown due to
72  * unexpected types.
73  *
74  * By moving the private attributes to a completely different type, this ID conflict will never
75  * occur.
76  */
77 struct PrivateAttributeMover : public IResourceTableConsumer {
78     bool consume(IAaptContext* context, ResourceTable* table) override;
79 };
80 
81 /**
82  * Resolves attributes in the XmlResource and compiles string values to resource values.
83  * Once an XmlResource is processed by this linker, it is ready to be flattened.
84  */
85 class XmlReferenceLinker : public IXmlResourceConsumer {
86 private:
87     std::set<int> mSdkLevelsFound;
88 
89 public:
90     bool consume(IAaptContext* context, xml::XmlResource* resource) override;
91 
92     /**
93      * Once the XmlResource has been consumed, this returns the various SDK levels in which
94      * framework attributes used within the XML document were defined.
95      */
getSdkLevels()96     inline const std::set<int>& getSdkLevels() const {
97         return mSdkLevelsFound;
98     }
99 };
100 
101 } // namespace aapt
102 
103 #endif /* AAPT_LINKER_LINKERS_H */
104